ESTRO 2022 - Abstract Book

S1228

Abstract book

ESTRO 2022

GTVCT were investigated. The maximal standardized uptake value (SUVmax) and metabolic tumor volume (MTV) were correlated with outcome. Results From December 2014 to September 2018, 70 oligometastatic patients were treated with VMAT SABR (median dose 45 Gy, range 30-50, in 3-5 fractions) at the Radiotherapy Unit of San Donato Hospital – Arezzo. Site of oligometastases were lung (28 patients), bone (20), lymphonodes (22) from lung (30), breast (28) and colorectal cancer (12). The mean GTVPETCT was significantly smaller than the mean GTVCT volumes (P = 0.04). Interobserver variability in target delineation was reduced if FDG PET CT was used. The proximal and distal margins of GTVCT volumes were altered by a mean of 0.5 ± 0.3 cm and 0.4 ± 0.2 cm, respectively. For 4D CT, ITV encompassed GTVPET CT in most cases: the GTVPET approximated to the ITV and the spatial mismatch is apparent between them. After a median follow up of 15.5 months (range 18.2- 32.8), 2 years local control (LC) was 90%. MTV and SUVmax did not significantly correlate with LC (p=0.16 and 0.4 respectively). Conclusion FDG PET/CT for dose planning improved target definition in oligometastatic patients. If VMAT SABRT is used, PET/TC parameters did not correlate with outcome. GTVPET CT can not replace ITV in spatial position and form for lung oligometastases. The advent of 4D PET/CT will improve the accuracy of contouring the perimeter for moving targets. B. Gil Haro 1 , S. Santana Jiménez 1 , J. Romero Fernández 1 , R. Molerón Mancebo 2 , R. Benlloch Rodríguez 1 , M. López Valcárcel 1 , M. Hernández Miguel 1 , I. Zapata Paz 1 , R. Rodríguez Romero 3 , L. Paisán Palacio 1 , A. Valcárcel Díaz 1 , P. Sarrión Rubio de la Torre 1 1 Puerta de Hierro University Hospital, Radiation Oncology, Madrid, Spain; 2 Aberdeen Royal Infirmary NHS Grampian, Radiation Oncology, Aberdeen, United Kingdom; 3 Puerta de Hierro University Hospital, Radiophysics, Madrid, Spain Purpose or Objective To assess the effectiveness and toxicity of single-fraction Lumbopelvic Bone Irradiation (LPBI) with Helical Tomotherapy (HT) in patients with widespread painful bone metastases. Materials and Methods Between May-2010 and Aug-2021, twenty-eight patients were treated with LPBI in our institution. Clinical characteristics: 17 males, 11 females; mean age: 65 yo (32-85). Most frequent primary tumors were prostate (10) and lung (9) adenocarcinoma. Radiation-therapy: PTV included all bones from the middle-third of the femur to D9-L4 (depending on the extent of disease) plus 5 mm symmetrical margin. A single-dose of 8 Gy was administered to all patients except 2 patients who had received prior irradiation in whom 6.5 Gy was administered. Patients were premedicated with 8 mg dexamethasone, 8 mg ondansetron and 500 cc saline-solution. Subjective pain relief and pain level (Visual Analog Scale– VAS) were evaluated. Statistics: Student’s-T-test. Results Median follow-up: 7 months (0-49). Pain relief: 26 patients. Mean VAS-score (at 3-weeks postradiotherapy), decreased from 6.39 (4-9) to 2.54 (0-7) (p < 0.001). In most of patients, the tolerance was mild (CTCAEv5.0-criteria). One patient suffered a tumor-lysis-syndrome after radiotherapy that was resolved with pharmacotherapy. None of 28 patients presented GU toxicity. Grade 1-2 toxicities were asthenia (8 patients), nausea (5 patients) and hematologic (10 patients). Only one grade 3 lymphopenia was observed. One- and two-years OS were 24% and 12%, respectively (Figure 1). Mean PTV: 3510cc (1934-7178cc). Mean V95: 93.2% (80-100%). Mean D95: 7.4 Gy (6-8.2Gy). Mean homogeneity index_RTOG: 1.08(1.01–1.15). Doses to OAR are shown in Figure 2. PO-1449 Single fraction Lumbopelvic Bone Irradiation with Helical Tomotherapy for metastatic bone disease